While doing some browsing I came across another useful SEO site: seomoz
In order to use the site you need:
- Google API key
- Yahoo API key
- Amazon API key
As its tools query a number of online resources using your tag, not theirs, which makes a lot of sense, especially as it’s a suite of free tools.
The tools available include ones for valuing links, checking keyword popularity and a range of other things that any budding DIY SEO expert should find useful.